Artificial tooth



April 26, 1938.

H. F. MOGRANE ARTIFICIAL TOOTH Filed May 4, 1935 Patented Apr. 26, 1938UNITED STATES PATENT OFFICE 8 Claims.

This invention relates to artificial teeth and particularly to certainimprovements in the formation of the occlusal surfaces of the posteriorteeth (bicuspids and molars) whereby numerous objections and defectsusually found in artificial dentures are largely eliminated. Thisinvention is applicable in cases requiring full upper and full lowerartificial dentures or in cases requiring full upper and partial lower,full lower and partial upper, or partial upper and partial lowerdentures. The term denture as employedin the following specification andclaims is intended to cover both removable dentures and stationarybridgework having articial teeth thereon.

The invention is illustrated in the accompanying drawing forming a parthereof and in which Figure 1 is a diagrammatic view illustrating theprinciple upon which the invention is based;

Figure 2 is a plan view of the occlusal surfaces of two adjacent teethembodying the features of the invention, this view illustrating onemolar and one bicuspid on the left side of a lower denture;

Figure 3 is a similar plan view looking toward the occlusal surfaces ofVtwo adjacent teeth on the right side of an upper denture;

Figure 4 is a side view of upper and lower dentures including molars andbicuspids formed according to the present invention and illustrating therelation of the same, this view being taken from the cheek orv buccalside thereof;

Figure 5 is a perspective view of a tooth involving the invention andshowing on an enlarged scale the arrangement of the grooves and cusps onthe occlusal surfaces; and

Figure 6 is a detail view illustrating the relation between the condyleheads of the lower jaw or mandible .and the cavities or sockets in whichsuch heads are arranged.

The drawing illustrates the invention applied to the case where all theposterior teeth in both the upper and lower jaw are replaced byartificial teeth. In such cases vit is the practice to provide twobicuspids and two molars on each side of the lower denture and the sameon each side of the upper denture. The upper denture is, of course,relatively fixed in position on the upper jaw while the lower denture ismounted on and moves with the lower jaw or mandible. The mandible isarticulated with the skull through the medium of the condyle heads whichengage in the glenoid cavities or fossae formed in the skull. Themandible is so articulated that it can move anteriorly and retrudeposteriorly to the starting point or it can move from this centraIstarting point in av lateral' direction toward the right and return tothe starting point or it can move laterally to the left and return tothe central starting point. This central point is generally referred toas the centric position and when 5 the lower jaw is in that position,the jaws are said to be in centric relation.

Whenv the mandible is in centric position the condyle heads thereof restcentrally in the glenoid fossae. When the mandible moves to the right 10from this centric position it rotates about a point displaced somewhatto the rear of the right condyle head and the left condyle head travelsforwardly in its socket or cavity. Likewise when the mandible moves tothe left from its centric 15 on describes an arc about one center andsimilarly 20 when the mandible moves to the left from its centricposition, every point thereon describes an arc about another center. Thelateral movements of the mandible to the right or left from its centricposition are on the average about 5 millimeters.

The present invention aims to provide artificial teeth having theirocclusal surfaces so formed as to permit the lateral movements of themandible to take place, particularly during mastication, withoutobjectionable cusp interference, the occlusal surfaces also being soformed as to produce' eiicient masticating surfaces. According to thisinvention the occlusal surfaces of the lower artificial teeth andocclusal surfaces of the upper articial teeth for full or partialdentures are provided with complementary grooves and ridges or rows ofcusps, which grooves and rows of cusps have a curved formationcorresponding with the 40 arcs of movement of the mandible as it moveslaterally from the centric position toward the right and toward the leftas above described. This arrangement will be clear from the accompanyingdrawing. The points A and B of Figure l repre- The upper ture. The upperleft hand portion of Figure l molars L.

represents in solid lines the occlusal surfaces 1 of two bicuspids L'and two molars I..2 and their relative positions on the left hand sideof a lower denture. The upper right hand portion of Fig- .ure 1 alsorepresents in dotted lines two upper bicuspids R,3 and two upper molarsR4 and their relative positions on an upper denture, the bicuspids R?and molars R4 being formed complementary to and arranged to cooperatewith the lower bicuspids and molars R and R. The upper left hand portionofFigure 1 further represents in dotted lines two upper blcuspids L3 andtwo upper molars L4, the occlusal surfaces of which cooperate with andare complementary to the occlusal surfaces of the bicuspids L' and Asbefore noted, the occlusal surfaces of the teeth are provided withgrooves and rows of cusps.

As shown, two series of spaced grooves are formed on the occlusalsurface of each tooth. In the Ydrawing the 'characters A designate oneseries of such grooves and thecharacters B' designate the otherr series.In the casey of `most'of said grooves both inclined side walls thereofare formed on one tooth, but where a groove passes across the denture atvthe margin of two adjacent teeth, the sides of the groove are formedpartly on one tooth and partly on the adjacent tooth. As shown in Figure1, the grooves A' are formed on arcs struck from the point A and thegrooves B are formedl on arcs struck from the point B. These points-Aand B,r as previously noted-correspond to the right and left centers ofrotation'of the mandible and the arcs struck yfrom the sameandgintersecting at the median line G form what is generally known asthe Gothic arch. I

It will be seen that one set of the Vcurved grooves above mentionedextends entirely across the occlusal surface of. each tooth in abuccallingual direction and that the other set extends entirely acrosssaid surface in an anterior-posterior direction. The two sets of groovesintersect each other. The portions of the occlusal surface of each toothbounded by these grooves are so shaped as to form a plurality of cusps Son each tooth. These cusps are preferably made Vpyramidal in form andthe sides of the grooves form the faces ofthe pyramids. The tops of thecusps are positioned inv curved lines corresponding to the curvature ofthe grooves so that when an upper and a lower denture-are brought -intoYengagement and' moved laterally, the rows of cuspsformed, on the' teethof one denture will occlude in thev grooves ofthe teeth on the opposingl denture. In other words, the cooperating teeth on the upper and lowerdentures areformed complementary to each other.

Some of the cusps S, at least one on each tooth, form complete orsubstantially. complete pyramids and othersi'orm`v portions of pyramids.The side faces of the pyranidal cusps, as beforestated, form the sidesof the grooves A', B', and said I face ofV each tooth will depend, ofcourse,'on the spacing of the grooves. This spacing should be such thatthe cusps will be of substantial size; In some cases it may be desirableto provide a tooth with a single groove extending Vone Way across thesame and several grooves extending the other way. y

From the foregoing it will 1 be apparent that when the mandible is movedlaterallyA to the right or left from its centric relation, the rows ofcusps s on the teeth of the upper and lower dentures will t into thegrooves of the teeth of the lower and upper dentures respectively. Inother words,

when the lower jaw is moved laterallytowardy the right or the left, therows of cusps'on each upper tooth and those on each lower tooth willmove freely through the grooves in the opposing teeth. By thisarrangement, cusp interference between the' teeth is obviated. As iswell known, cusp interference, technicallyy termed cusp trauma, presentsone of the chief difficulties of artificial dentures. This difficulty isovercome by the present arrangement since the mandible can movelaterally in either direction from its centric position with theocclusal surfaces of the teeth in contact throughout'the entire movementand lno substantial interference between the cusps will occur andtipping of the plates or sliding `of the A same on the jaws duringmastication is practically obviated. I. f

Furthermore, the type of tooth as above `described presents an occlusalsurface that has the greatest amount of cutting and grinding efficiencyin the mastication of food. As will be seen, each tooth of this type hasapproximately nine small cusps which cooperate with the grooves on theopposing tooth. This produces a very effective masticating arrangement.Also, -the grooves on each tooth, all` of which` extend to the ledgesthereof, afford a suilicient lnumber of escape gates or passages Vbywhich thefood can escape from the occlusal surfaces during mastication,which effectively prevents jamming of thefood on or between the teeth.

Itv willv be understood thatk artificial teeth made in accordance withmy invention maybe used in stationary bridgework as well as in removabledentures.

Another advantage ofthe invention is found in the ease by which thepractitioner canplace the teeth of this invention on his articulator informing the ,set-up for an artificial denture.

-Thc anterior-posterior grooves afford guides for making such set-up.VThus the first molar can l readily beplaced in position so-that thegroove on the occlusal surface (lingual third) thereof`A Iis inalignment with the occlusal groove (buccal third) on the second molar.Similarlythe second bicuspid can be lined up with the first molar f andthe first bicuspid with the second bicuspid. By this means the operationof making the "set- 1 up is greatly facilitated.

It is well known, of course, that thev surfaces of the glenoid cavitiesareeso inclined that during the protrusive movement of the mandible therear condyle heads thereof move downwardly to a slight extent. 'I'hisinclination is on the averageabout 33. Also, due to this vinclination ofthe glenoid cavities, it follows that whenthe mandible is movedlaterally toward the left from its centric l position and the rightcondyle head moves forwardly, as heretofore described, the right side ofthe mandible moves downwardly to a slight extent due to the inclination.of the glenoid cavity.

Similarly the left side of the mandible moves downwardly to a slightextent, when themandible is moved toward the right from its centricposition. However, these slight downward movements of the mandible dueto the shape of the glenoid cavities do not materially affect theprinciple of the present invention and do not prevent effective-occlusion of the upper and lower dentures or materially interfere withthe free lateral movements of the same.

Having thus described the invention, what is claimed as new and desiredto be secured by -Letters Patent is:

1. An artificial denture for an upper or lower jaw including a `toothhaving its occlusal surface I provided with one series of curved groovesextending entirely across the same in a lingualbuccal direction, andalso with a second series of curved spaced grooves extending entirelyacross the same from the front or anterior to the rear or posterior sidethereof, said iirst named grooves being formed on an arc struck from thecenter of rotation of the lower jaw as itmoves laterally from centricposition in one direction, and said second series of grooves beingformed on arcs struck from the center of rotation of the lower jaw as itmoves laterally from said centric position in the other direction, saidocclusal surface being bounded by said grooves and being shaped to forma plurality of cusps, the side walls of the grooves forming sides ofsaid cusps.

2. In combination, cooperating dentures for an upper and a lower jaw,each denture including an artificial tooth arranged to cooperate with atooth in the other denture, the tooth in said lower denture having itsocclusal surface provided with a series of curved spaced groovesextendingentirely across the same from the lingual to the buccal sidethereof, andalso with a series of curved spaced grooves extendingentirely across the same from the anterior to the posterior sidethereof, said grooves in one series being formed on arcs struck from thecenter of rotation of the lower jaw as it moves laterally from centricposition toward the`right and the other series 'of grooves being formedon arcs struck from the center of rotation of the lower jaw as it movestoward the left from said centric position, the portions of saidocclusal surface bounded by said grooves being shaped to form curved'rows of cusps extending' in a lingual-buccal direction across saidtooth, the side Walls of said grooves forming sides of the cusps, thetooth in said upper denture having its occlusal surface provided withcurved spaced grooves and rows of cusps complementary to and arranged toocclude respectively with the rows of cusps and grooves on said rstnamed tooth, whereby lateral movement of the Y lower jaw toward theright or left fromV its centric relation is permitted without cusp interference between the teeth of said dentures.

3. An artificial tooth for a lower jaw having its occlusal surfaceprovided with a series of curved spaced grooves extending entirely fromthe alingual to the buccal side thereof, said grooves being formed onarcs struck from the center of rotaf rear thereof, said last namedgrooves beingl formed on arcs struck from the center of rotation of thejaw as it moves from itsy centric position toward the left, the portionsof said occlusal surface bounded by said grooves being shaped t0 formcusps thereon, the side walls of said grooves forming sides of thecusps.

4. An artificial denture for an upper or lowerl each of said teethhaving its occlusal surfaceA provided with a series of curved spacedgrooves extending entirely across the same in a lingual buccaldirection, said grooves being formed on arcs struck from one vcenter ofrotation of tl'iel lower jaw each of saidteeth also having its occlusalsurface provided with a series of curved spaced grooves extendingentirely across the same in a posterior-anterior direction, said lastnamed grooves being formed on arcs struck from the other center ofrotation of the lower jaw, the portions of the occlusal surfaces boundedby said grooves in each of said teeth being shaped to form cusps, theside walls of said grooves forming sides of the cusps, said cusps oneach tooth being arranged in rows extending in a lingual-buccaldirection across the tooth and also in rows extending in ananterior-posterior direction across the tooth.

5. A construction as defined in claim 4 in which one of theposterior-anterior grooves in one tooth is arranged in alignment with aposterior-anterior groove in an adjacent tooth.

6. In combination, cooperating artificial dentures for an upper and alower jaw, each denture having a plurality of teeth thereon arranged tocooperate with the teeth of the other denture,

' each tooth 'on said lower denture having its occlusal surface providedwith a series of curved spaced grooves extending in a lingual-buccaldirection entirely across the same, said grooves being formed on arcsstruck from one center of rotation of the lower jaw. and also having onits occlusal surface a series of curved spaced grooves extending in ananterior-posterior direction entirely across the same, said last namedgrooves being formed on arcs struckfrom the other center of rotation ofthe lower jaw, the

-,portions of theocclusal surfaceofeah. of. saic i teeth bounded by saidgroovesbeing'shapedto" form cusps, the side walls of said groovesforming sides of the cusps, said `cusps being arranged in rows extendingin a lingual-buccal direction and also in rows extending in ananterior-posterior direction, the teeth on said upper denture lowerteeth and upper teeth respectively being l arranged to occlude with andmove in the anterior-posterior grooves of the opposing teeth when thelower jaw is moved laterally in the other direction from its centricposition.

7. An artificial denture for a posterior tooth in an upper or lower jaw,said denture having two series of parallel curved grooves extendingentirely across the occlusal surface thereof, one series of said groovesbeing formed on arcs struck from the center Vof rotation of the lowerjaw as it moves laterally in one direction from the centric pos'ition,the other series of said grooves being formed on arcs struck from thecenter of rotation of the lower jaw as it moves late rally from centricposition in a direction opposite to said one direction, the occlusalsurface of said denture the center of rotation about which the lower jawrotates inmoving from its centric position n one direction and the otherseries of said grooves being formed on arcs struck from the center ofrotation o! the lower jaw as it moves laterally from centric position ina direction opposite from said ilrst named direction, said two series ofgrooves intersecting and forming intersecting side enclosing yportionsof said occusal surface, thereby forming rows of cusps.

` HENRY F. MCGRANE.

